R91.1 – Solitary pulmonary nodule

Discover the clinical description, billing details, and commonly used R91.1 - Solitary Pulmonary Nodule codes. Learn about its diagnosis, synonyms, and evaluation methods.

By Katherine Ellison on Aug 8, 2025.

Fact Checked by Ericka Pingol.

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R91.1 diagnosis code: Solitary pulmonary nodule

A solitary pulmonary nodule (SPN) refers to a round or oval lesion that measures less than 3 centimeters in diameter and is completely surrounded by lung tissue. This is coded as R91.1 solitary pulmonary nodule in ICD-10-CM.
These nodules are typically found incidentally on diagnostic imaging, such as a chest radiography or computed tomography (CT) scan. They may be identified when healthcare providers are evaluating for respiratory system diagnoses or symptoms, signs, and abnormal clinical and laboratory findings, or through function studies.
Most solitary pulmonary nodules are non-cancerous (benign) and may be caused by various factors, including infections, scars, inflammation, or non-infectious granulomas.
However, some SPNs can indicate lung cancer, or other respiratory system diagnoses, so further evaluation and diagnostic tests are necessary to determine their nature and potential malignancy. A positron emission tomography (PET) scan is often used to assess metabolic activity and rule out other abnormal findings or other organ involvement.

Is R91.1 billable?

Yes, the ICD-10-CM code R91.1 is a billable code. Healthcare providers can use this code to document and bill for the diagnosis of a solitary pulmonary nodule encountered during a patient's care. Reimbursement and coverage for medical services related to evaluating and managing SPNs may vary depending on the payer, specific circumstances, and any associated procedures or diagnostic-related group (DRG) assignments.

Clinical information

Solitary pulmonary nodules are typically discovered incidentally during routine chest radiography or other diagnostic imaging of lung studies.
Diagnostic evaluation and management depend on the characteristics and size of the nodule, patient risk factors, and clinical judgment. In cases of abnormal findings, particularly abnormal findings on diagnostic imaging, the final diagnosis may require integration of multiple diagnostic tests.
Key clinical considerations for SPNs include determining the likelihood of malignancy and deciding whether further investigations or interventions are necessary to exclude lung cancer or other nonspecific abnormal findings.

Additional tests commonly used in the evaluation of SPNs include:

Positron emission tomography (PET) scan
CT-guided biopsy or needle aspiration
Follow-up imaging at specific intervals to monitor for abnormal results
Surgical excision or resection, if warranted, especially when malignancy is suspected

Factors that influence the evaluation and management of SPNs include:

Nodule size
Patient's age and medical history
Smoking history
Radiographic features of the nodule (such as small round mass or irregular margins)
Presence of symptoms or associated abnormal clinical or laboratory findings

Synonyms include

Solitary lung nodule
Pulmonary coin lesion
Solitary pulmonary mass
Solitary pulmonary opacity
Single lung lesion

Other ICD-10 Codes Commonly Used for Solitary Pulmonary

R91.2 - Nonspecific pulmonary infiltrate
R91.8 - Other nonspecific findings on diagnostic imaging of lung
R91.9 - Unspecified nonspecific finding on diagnostic imaging of lung
R97.0 - Elevated cancer antigen 125 [CA 125]
R97.1 - Elevated cancer antigen 19-9 [CA 19-9]
R97.2 - Elevated carcinoembryonic antigen [CEA]
R97.8 - Elevated tumor markers
R97.9 - Elevated tumor marker, unspecified

Commonly asked questions

Diagnostic tests commonly used to evaluate SPNs include chest imaging (X-ray, CT scan), PET scan, CT-guided biopsy, needle aspiration, and surgical excision or resection, if warranted.

While most solitary pulmonary nodules are benign, some can be cancerous. Further evaluation, including diagnostic tests and clinical judgment, is necessary to determine their nature and potential malignancy.

Risk factors associated with SPNs include smoking history, older age, exposure to certain occupational or environmental hazards, and underlying lung conditions. However, SPNs can also occur in individuals without any apparent risk factors.

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